The broad, LONG TERM OBJECTIVE is to improve the therapy of ethanol (EtOH) induced diseases of excitable tissue via better insight into mechanisms. As many EtOH studies can't be done accurately in man, an animal model is needed. Our MODEL is cat esophagus since it is: a) similar to man's; b) accessible for repeated physiologic studies; c) one in which biochemical & physiological changes can be correlated d) an organ for simultaneously studying: smooth muscle (lower esophagus[LE]), striated muscle (upper esophagus[UE]), & specialized smooth muscle (lower esophageal sphincter [LES]]). We characterized EtOH-induced esophageal dysmotility (EIED) in man, developed an animal model for it, & studied mechanisms. In men, acute EtOH decreases LES pressure (LESP) & LE pressure (LEP). But, during withdrawal from EtOH, LESP & LEP increased. In cats, parallel findings were noted in LES & LE in males only, suggesting that female sex hormones attenuate EtOH's chronic effects. UE pressure (UEP) responded differently than LEP in cats: acute EtOH had no effect on UEP while UEP rose during both chronic EtOH & withdrawal. Of two popular hypotheses for chronic EtOH's effects, up-regulation of neurotransmitter receptors, or perturbation of Ca2+ regulation, our data failed to support the first. The second, which now needs to be tested, is plausible since: 1) cytosolic Ca2+ concentration ([Ca2+]i) is critical to excitable tissue function; 2) EtOH disrupts Ca2+ regulation in brain & vascular smooth muscle; 3) acute EtOH decreases Ca2+ influx into LES & LE slices but only minimally increases influx into UE (our data). HYPOTHESIS: 1. During Acute EtOH: [a] in smooth muscle, a drop in Ca2+ influx & [Ca2+]i lowers LESP & LEP. [b] in striated muscle, a rise in Ca2+ influx occurs, but [Ca2+]i fails to increase sufficiently to elevate UEP. 2. During Chronic EtOH: [a] in smooth muscle, Ca2+ channels up-regulate so that in withdrawal, elevated [Ca2+]i raises LESP & LEP. [b] in striated muscle, Ca2+ influx now increases sufficiently to increase [Ca2+]i & UEP rises. {{ In 1 & 2 above, muscle is EtOH's primary target.}} 3. In females, sex hormones attenuate the EtOH-induced increases in [Ca2+]i, which results in smaller pressure changes in withdrawal.
Our SPECIFIC AIMS are to evaluate: 1. The effect of acute EtOH on [a] muscle contractions ({{in vitro strips & dispersed muscle cells}}; in vivo motility) [b] Ca2+ parameters in LES, LE & UE: [i]45Ca2+ influx into esophageal slices {{ or cells }}; [ii] [Ca2+]i in cells using fluorescent dyes. [iii] [3H]nitrendipine binding to Ca2+ channels in slices. 2. The effect of chronic EtOH on LES, LE & UE as in Aim #1. 3. The role of female sex hormones in EIED by measurement of [a] esophageal motility in alcoholic women & ovariectomized cats; [b] the effect of female sex hormones on {{muscle contraction}} & Ca2+ parameters in cells, slices & strips. {{ In all Aims, Ca2+ data will be correlated with muscle contraction data}}. These experiments should not only reveal the mechanism for EIED but also, confirm that functional changes in excitable tissue correlate with altered C12+ regulation.
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